Many electronic devices, such as laptops, tablet computers, smartphones, and the like, use rechargeable batteries to provide power to one or more electronic components. A number of electronic devices use thin film batteries as the power source because of the many advantages it has over other batteries. For example, lithium ion thin film batteries which have a potential high energy density while maintaining a relatively compact configuration.
A lithium thin film battery's performance is significantly affected by properties of the cathode electrode. Currently, a number of lithium ion thin film batteries use a lithium cobalt oxide (LiCoO2) cathode that has a thickness of 10 micron or thinner. These batteries have a capacity of about 2 mAh or less. One approach to increase battery capacity, and thus increase the number of applications the battery can be used for, is to increase the thickness of the LiCoO2 film. Another is to increase the quality of the cathode material. In both of these approaches, it may be useful to anneal the thin film cathode material.
In a typical annealing process, after the LiCoO2 film has been deposited on a substrate, the substrate is loaded into a furnace at a temperature as high as 700 C for a few hours. This thermal annealing process is useful to change the crystalline structure and improve the crystal quality of the LiCoO2 film. Unfortunately, current annealing processes have several disadvantages, including: the high temperature used significantly limits possible substrate selections, as the substrate material has to be able to stably withstand at the anneal temperature; practically mass production may be difficult; increased production costs related to the use of a high temperature annealing process. Example embodiments include annealing processes that allow the improvement of the crystal quality of LiCoO2 cathode material in thin film batteries, as well as other thin film materials, without subjecting the substrate on which the film is deposited having to withstand the high temperature conditions typically associated with annealing processes.